1. Field of the Invention
The present invention relates to an optical information recording medium on which recording/reproducing of information is made by means of laser beam application, and, in particular, to an optical information recording medium having therein both a RAM area on which information recording, reproducing and erasing can be made and a ROM area from which only information reading can be made (such a type of an optical information recording medium will be referred to as a ‘hybrid optical information recording medium’, hereinafter).
2. Description of the Related Art
Japanese patent registrations Nos. 2596474, 2596477, 2597491, Japanese laid-open patent applications Nos. 4-146537, 4-146536 and 3-241538 disclose such a type of hybrid optical information recording medium, for example.
In case of manufacturing such a type of hybrid optical information recording medium utilizing organic pigment as in well-known CD-R, DVD-R, and so forth, when pre-pits in the ROM area are filled up with a pigment material, there has been no reference value in amount of pigment material to be used therefor. However, in case of the amount of pigment material is too much, various problems such as that in which the modulation degree becomes lowered, symmetry becomes degraded, and so forth, may occur in the resulting product of the recording medium.